1. Field of the Invention
This invention relates to a base station and a terminal configuring a wireless network, and a communication method. This invention relates to the base station, terminal, and communication method suitable for a multiple access protocol for maximizing a utilization of a frequency band and realizing a maximum throughput and a minimum delay, for example.
2. Description of the Related Art
The multiple access protocol in a wireless network is expected to maximize the utilization of the frequency band and realize the maximum throughput and the minimum delay (xe2x80x9cMobile Wireless Computing: Challenge in Data Managementxe2x80x9d by T. Imielinski and B. R. Badrinacth, Commun. ACM, vol. 37, pp. 18-28, October 1994 (related art 1)).
Several studies have been made on the multiple access protocol for broadcast channels, e.g., a wireless network, communication satellite, etc. (xe2x80x9cData Networksxe2x80x9d by D. Bertsekas and R. Gallager, Second Edition, Prentice-Hall, 1992 (related art 2)), (xe2x80x9cMultiaccess Protocols in Packet Communication Systemsxe2x80x9d by F. A. Tobagi, IEEE Trans Commun. Vol. COM-28, pp. 468-488, April 1980 (related art 3)), (xe2x80x9cThe ALOHA Systemxe2x80x94Another Alternative for Computer Communicationsxe2x80x9d by N. Abramson in 1970 Fall Joint Comput. Conf. AFIPS Conf. Proc. Vol. 37. Montvale, N.J.: AFIPS Press, pp. 281-285, 1970 (related art 4)), (xe2x80x9cPacket Switching in Radio Channels: Part Ixe2x80x94Carrier Sense Multiple-Access Modes and their Throughput-Delay Characteristicsxe2x80x9d by L. Kleinrock and F. A. Tobagi, IEEE Trans. Commun., vol. COM-23, pp. 1400-1416, December 1975 (related art 5)), (xe2x80x9cPacket Switching in Radio Channels: Part IIxe2x80x94the Hidden Terminal Problem in Carrier Sense Multiple-Access and the Busy-Tone Solutionxe2x80x9d by F. A. Tobagi and L. Kleinrock, IEEE Trans. Commun., vol. COM 23, pp. 1417-1433, December 1975 (related art 6)), (xe2x80x9cTree Algorithms for Packet Broadcast Channelsxe2x80x9d by J. I. Capetanakits, IEEE Trans. Information Theory, vol. IT-25, September 1979 (related art 7)).
Among recent studies on the multiple access method using a wireless channel, as a distributed control method, FAMA for confirming an acquisition of a transmission right between a sender terminal and a receiver terminal for preventing a drop in a throughput due to a hidden terminal is proposed by Fullmer, etc. in addition to CSMA/CD (Carrier Sense Multiple Access/Collision Detection) (xe2x80x9cFloor Acquisition Multiple Access (FAMA) for Packet-Radio Networksxe2x80x9d by C. L. Fullmer and J. J. Garcia-Luna-Aceves, Proc. ACM SIGCOM 95, Cambridge, Mass., Aug. 30-Sep. 1, 1995 (related art 8)). FAMA-PJ (Floor Acquisition Multiple Access with Pauses and Jamming), an improved version of the FAMA, in which jamming is provided for preventing a propagation delay and a collision due to a transmission timing in the CSMA/CD, is proposed (xe2x80x9cFAMA-PJ: A Channel Access Protocol for Wireless LANsxe2x80x9d by C. L. Fullmer and J. J. Garcia-Luna-Aceves, Proc. ACM MOBICOM 95, pp. 76-85, 1995 (related art 9)).
As a centralized control method, CARMA (Collision Avoidance and Resolution Multiple Access) for transmitting a control command of the FAMA using a stack algorithm (also called as a tree algorithm) is proposed by R. Garces, etc. (xe2x80x9cFloor Acquisition Multiple Access with Collision Resolutionxe2x80x9d by R. Garces and J. J. Garcia-Luna-Aceves, Proc. ACM MOBICOM 96, pp. 187-197, 1996 (related art 10)). CARMA-NTG (Collision Avoidance and Resolution Multiple Access Protocol with Non-Persistent Trees and Transmission Groups), in which a node acquired a transmission right by the CARMA configures a transmission group, is also proposed by R. Garces, etc. (xe2x80x9cCollision Avoidance and Resolution Multiple Access with Transmission Groupsxe2x80x9d by R. Garces and J. J. Garcia-Luna-Aceves, Proc. IEEE INFOCOM ""97, pp. 134-142, 1997 (related art 11)).
Further, DQRUMA for making a reservation of a data transmission channel by an aloha method with a slot or the stack algorithm and, when the data transmission channel is obtained, maintaining the reservation using a piggyback request is proposed (xe2x80x9cDistributed-Queuing Request Update Multiple Access (DQRUMA) for Wireless Packet (ATM) Networksxe2x80x9d by M. J. Karol, Z. Liu, and K. Y Eng, Proc. of ICC ""95, pp. 1224-1231, June, 1995 (Related art 12)).
Especially, the DQRUMA for reserving a data slot by the stack algorithm is an efficient protocol, which is stable even at a time with a high load.
The DQRUMA (related art 12); which is a basis of this invention; is outlined.
The DQRUMA is an efficient channel access protocol with a request-time-allocation type, which is designed for a packet in a fixed length.
FIG. 12 shows a configuration chart of time slots in the DQRUMA protocol.
In the DQRUMA, a transmission between terminals is relayed by a base station using a time slot 1201. Each of time slots 1202 in an up-link, transmitted by the terminals and received by the base station, is divided into a request access channel 1204 and a data transmission channel 1206. A piggyback request flag 1205 is used by a user, who has obtained a data transmission channel once, for adding a request information of a data transmission consecutively. Each of time slots 1203 in a down-link transmitted by the base station and received by the terminals is divided into a request access response channel 1207, a data transmission permission channel 1208, and a data transmission channel 1209. In the base station, there is a request table with an entry for each of all the terminals in a cell. Each entry in the table includes a terminal identifier and a transmission request information (if the terminal still maintains transmission data). The DQRUMA protocol can be divided into a request access phase and a data transmission phase.
At first, explanations are made on the request access phase.
When the transmission data are generated, the terminal transmits a transmission request (of which content is the terminal identifier) to the base station using the request access channel 1204 in an up-link. The request access channel, i.e., a random access channel, is shared by all the terminals. Therefore, a collision can occur in the request access channel 1204, and the aloha method with a slot or a binary-stack algorithm is used to prevent the collision. When the transmission request is received from the terminal normally, the base station sets a flag indicating that the terminal maintains transmitting data in the request table. The base station reports that the transmission request is accepted by broadcasting the received terminal identifier using the request access response channel 1207 in the down-link. When the acceptance of the request is reported, the terminal receives the data transmission permission channel 1208 in the down-link, while waiting for an allocation of the data transmission channel 1206 to the terminal.
Explanations are made on the data transmission phase.
The base station selects one of the terminals with the transmission request in the request table in accordance with a requested data transmission policy, e.g., a round robin, and permits the data transmission in a next time slot. This is reported by broadcasting the terminal identifier using the data transmission permission channel 1208 in the down-link. When the terminal transmits the data using the data transmission channel 1206 in the up-link, the terminal reports to the base station if any transmitting data are left by the piggyback request 1205. The base station checks the piggyback request 1205, and updates the entry in the request table.
When there is no transmission request in the request table, the base station reports that the data transmission channel 1206 in the next up-link is converted to a plurality of request access channels 1204 using the data transmission permission channel 1208 in the down-link. The data transmission channel 1209 in the next down-link is also converted to a plurality of request access response channels 1207 synchronously for responding to a plurality of request accesses.
In the DQRUMA protocol, the collision occurs only in the request access channel 1204, and the piggyback request 1205 can be transmitted without the collision. Therefore, the collision of the request in the random access protocol is reduced dramatically, and the system capacity at the time with a high load is improved tremendously. Further, since the base station appoints the terminal which transmits the data for each of the slots, the DQRUMA can satisfy requests of various services.
The DQRUMA is a method mainly related to the request access channel 1204 in the data transmission channel, and no concrete proposal is made on an allocation method of the data transmission channel 1206 for the accepted request. Further, no discussion is made on the transmission between cells. Therefore, a protocol in the cell for the transmission between the cells is not proposed.
As the channel allocation method using the channel request method of the DQRUMA, a method for transmitting data with requests of various services, voice, etc. is proposed by Yamamoto, Machida, and Ikeda (xe2x80x9cAccess Control Scheme for Multimedia Wireless ATM (Asynchronous Transfer Mode) Local Area Networksxe2x80x9d by M. Yamamoto, S. Machida, and H. Ikeda, Proc. of 3rd Asia-Pacific Conference on Communications (APCC ""97), Sydney, Australia, December, 1997 (Related art 13)).
As stated, in the DQRUMA, no consideration is made on a direct transmission and receipt of the data (also called as a direct communication) between mobile terminals in the communication within the cell. Further, no consideration is made on an omission of a data transmission channel in the transmission between the cells, either. Therefore, the utilization method of the channel is wasteful. Further, there remains the possibility of improving the performance and lowering the delay.
This invention is most close to the DQRUMA among the related arts. However, this invention is also related to RAMA proposed by Amitay (xe2x80x9cResource Auction Multiple Access (RAMA): Efficient Method for Fast Resource Assignment in Decentralized Wireless PCS (Personal Communications Services)xe2x80x9d by N. Amitay, Electron. Lett., vol. 28, no. 8, pp. 799-801, Apr. 9, 1993 (Related art 14)), PRMA (Packet Reservation Multiple Access) proposed by Goodman, etc. (xe2x80x9cPacket Reservation Multiple Access for Local Wireless Communicationsxe2x80x9d by D. J. Goodman, R. A. Valenzuela, K. T. Gayliard, and B. Bamamurthi, IEEE Trans. Commun., vol. COM-37, pp. 885-890, August 1989 (Related art 15)), PRMA++ proposed by Vile (xe2x80x9cA Reservation Multiple Access Scheme for an Adaptive TDMA (Time Division Multiple Access) Air Interfacexe2x80x9d by J. De Vile, Proc. Fourth WINLAB Workshop on Third Generation Wireless Information Networks, N. J., 1993 (Related art 16)), SIR (Service Integration Radio Access) proposed by Anastasi, etc. (xe2x80x9cA Bandwidth Reservation Protocol for Speech/Data Integration in TDMA-Based Advanced Mobile Systems,xe2x80x9d by G. Anastasi, D. Grillo, L. Lenzini, and E. Mingozzi, Proc. IEEE INFOCOM ""96, San Francisco, Calif., 1996 (Related art 17)), and SIP (Service Integration for Radio Access)++ proposed by Anastasi, etc. (xe2x80x9cAn Access Protocol for Speech/Data/Video Integration in TDMA-Based Advanced Mobile Systemxe2x80x9d by G. Anastasi, D. Grillo, L. Lenzini, and E. Mingozzi, IEEE Journal on Selected Areas in Communications, Vol. 15, No. 8, pp. 1498-1510, October, 1997 (Related art 18)).
According to one aspect of this invention, a base station includes a time slot configuration determiner for determining a time slot configuration dynamically.
According to another aspect of this invention, a terminal includes a direct normal receipt judging unit for judging that data are received from another terminal directly, and a direct normal receipt report transmitter for transmitting a direct normal receipt report indicating a receipt of the data from another terminal to a base station.
According to another aspect of this invention, a terminal includes a channel sequence report judging unit for judging a report of a channel sequence transmitted by a base station, and a channel sequence controller for controlling the channel sequence based on the report of the channel sequence.
According to another aspect of this invention, a communication method, in which data are communicated between a terminal and a base station using a time slot including a plurality of channels, is provided. The communication method includes a step of selecting at least a channel among the plurality of channels and configuring the time slot based on the selected channel.
Further features and applications of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Other objects features, and advantages of the invention will be apparent from the following description when taken in conjunction with the accompany drawings.